Recently, a thermoelectric power-generating technology for which the system is simple and can be down-sized has been specifically noted as a power recovery technology for unharnessed exhaust heat that is generated from fossil fuel resources and others used in buildings, factories, etc. However, thermoelectric power generation is, in general, poorly efficient in power generation, and therefore, studies and developments are being actively made for improving power generation efficiency in various companies and research institutes. For improving power generation efficiency, it is indispensable to enhance the efficiency of thermoelectric conversion materials, and for realizing it, it is desired to develop materials having a high electrical conductivity comparable to that of metals and having a low thermal conductivity comparable to that of glass.
A thermoelectric performance can be evaluated by a figure of merit Z (Z=σS2/λ). Here, S means a Seebeck coefficient, σ means an electrical conductivity (reciprocal of resistivity), and λ means a thermal conductivity. Increasing the value of the figure of merit Z improves the power generation efficiency, and for enhancing the efficiency in power generation, it is important to find out a thermoelectric conversion material having a large Seebeck coefficient and a large electrical conductivity a, and having a small thermal conductivity λ.
As described above, investigations for improving power generation efficiency are needed while, on the other hand, thermoelectric conversion devices that are now produced are poor in mass-productivity and the power generation units therein are expensive. Consequently, for further disseminating the devices in use in large areas, for example, in installation thereof on the wall surface of buildings, production cost reduction is imperative. In addition, thermoelectric conversion devices that are produced at present are poorly flexible, and therefore flexible thermoelectric conversion devices are desired.
Given the situation, Patent Literature 1 discloses, for the purpose of improving power generation efficiency and for efficient production, a method for producing a thermoelectric conversion device that comprises a step of applying a solution to be a material of a p-type or n-type organic semiconductor device, onto a support having an insulator, by coating or printing thereon followed by drying it. On the other hand, in Non-Patent Literature 1, an investigation is made, using a composition prepared by dispersing, as a thermoelectric conversion material, bismuth telluride in an epoxy resin, and forming the composition into a film by coating, thereby producing a thin-film thermoelectric conversion device. Further, a thermoelectric material that comprises an organic thermoelectric material such as a polythiophene or a derivative thereof and an inorganic thermoelectric material which are integrated in a dispersed state (Patent Literature 2), and an organic-inorganic hybrid thermoelectric material that comprises, as an inorganic thermoelectric material, inorganic particles having an average particle diameter of 1 to 100 nm and being substantially free from a protective agent that may be a factor obstructing carrier transfer, and an organic thermoelectric material (Patent Literature 3) are being investigated.